الفهرس 
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Abstract
This study was designed to investigate the effect of potassium, calcium
and humic acid and the effect of the interaction on vegetative growth tuber yield, and its components, tuber quality characters and chemical constituents of potato.
The experiments were conducted in a private farm in El-Nubaria region, El Beheira Governorate, Egypt. Field experiments were conducted during the summer seasons of 2016 and 2017, to study the physiological response of the growth, tuber yield and its quality of
potato to different rat of foliar application of potassium and calcium as well as humic acid concentrations that added as drench after full emergency of potato plants and as a foliar application. The potato cultivar Hermes was used in these experiments. The
experimental treatments were arranged in a split-split-plots system in a Randomized Complete Blocks Design of forty-eight combination treatments replicated three times, in the two
growing seasons.
Two field experiments were carried out during the summer seasons of
2016 and 2017, to explore effect of four rates of potassium, as K2SO4 :0, 1, 2 and 3%, four rates of calcium as Ca (NO3)2 :0, 1.5, 2.0 and 2.5% and three rates of humic acid: 0, 1000 and
2000 ppm, as well as their interactions on growth, yield and its quality of potato. Data were recorded of some vegetative growth characters, tuber yield and its components, quality
characters and chemical constituents of potato tuber. Data were recorded of some vegetative growth characters, tuber yield, and its components, quality characters and chemical constituents of potato tuber. The obtained results could be summarized as follows:
5.1- Vegetative Growth characters
Potato plants that sprayed with potassium sulfate at the rate of 3% achieved the highest means value of plant height, number of leaves plant-1
, canopy fresh weight, dry matter
and leaf area plant-1
, in both seasons. However, the potassium levels did not reflect any
significance effect in the case of stems number plant-1 , in both seasons.
Spraying potato plants with Ca fertilizer rates lead to significant increases in plant height, number of leaves plant-1, canopy fresh weight, total leaf area plant-1, and foliage dry
matter compared with the control treatment. The highest mean values of all vegetative growth
characters were obtained by using Ca fertilizer at the rate of 2.5%.
Raising the humic acid concentration up to 2000 ppm gave the highest mean values of vegetative growth characters: plant height, number of leaves plant-1
, canopy fresh weight, dry
matter and leaf area plant-1
, in both seasons. Nevertheless, in the case of main stems number
plant-1, the results showed that sprayed potato plants with humic acid at any rate had no significant effect, in the two seasons.
On the other hand, potato plants that received potassium sulfate at the rate of 3% with calcium nitrate 2.5% and humic acid at the rate of 2000 ppm achieved the highest mean
values of vegetative growth characters: plant height, main stems number plant-1
, number of leaves plant-1
, canopy fresh weight, dry matter and leaf area plant-1, in both seasons.
5.2- Tubers Yield and Its Components
Increasing the K rates that used 3% was associated with corresponding successive
significant increments in tubers number of plant-1, tuber weight of plant-1
; total yield feddan-1
61 and large size grades % characters, but it led to a lower the percentage of medium and small
tubers size grade and the number of tubers in 10 kg characters, in both growing seasons.
Foliar spraying of potato plants with calcium nitrate at the rate of 2.5% gave the highest mean values of tubers number plant-1, tuber weight of plant-1
, total yield feddan-1
, in both seasons and the number of tubers in 10 kg, in the second season only. In addition, spraying potato plants by calcium fertilizer leads to a significant decrease in the percentage of the large tuber, in both seasons. However, calcium fertilizer levels did not have a significant effect on the percentage of medium tuber and number of tubers in 10 kg, in both growing
seasons.
The results, indicated that addition of humic acid at rate 2000 ppm achieved the
highest mean values of number of plant-1
, tuber weight of plant-1, total yield feddan-1 and large
and medium size grades %, in both seasons, with one exception in the case of the percentage of the medium tuber, in the second season, where the highest value achieved with the application of humic acid at 1000 ppm. While, the addition of humic acid significantly
decreased the percentage of small tubers and the number of tubers in 10 kg, in both seasons.
The interaction effects showed that potato plants that treated by potassium sulfate at the rate of 3% with calcium nitrate 2.5% and humic acid at the rate of 2000 ppm obtained significant increases in the average of tubers yield and its components: number of plant-1
,tuber weight of plant-1 and total yield fed-1, in both seasons. In addition, the results showed that the highest mean value of potato large tuber percentage and the lowest ones of medium
and small tuber percentages and the number of tubers in 10-1kg were obtained from potato plants that sprayed by high levels of potassium (3%), unfertilized by calcium and untreated by humic acid, in both seasons.